Small Size-induced Plasticity and Dislocation Activities on Non-charge-balanced Slip System of Ionic MgO Pillars.

We observed the small-size-induced hardening and plasticity of brittle ionic MgO as a result of abnormally triggered dislocation gliding on a non-charge-balanced slip system. The indentation tests of <111> MgO pillars revealed an increased hardness with decreasing pillar size, and the tips of the pillars that were <= 200 nm were plastically deformed. The in situ compression tests of <111> MgO nanopillars in transmission electron microscopy verified aligned dislocation-mediated plasticity on the {111}<110> and {100}<110> systems rather than the charge-balanced {110}<110> slip system.